When a plurality of solenoid valves are collectively attached to a manifold for use, a manifold solenoid valve is used. The “manifold” is also called a “manifold base” or simply a “base”. The base is provided with a common air-supply flow path for supplying compressed air to each solenoid valve, and a common exhaust flow path for exhausting, to the outside, the compressed air that has been exhausted from each solenoid valve. An indirect actuating type solenoid valve activated by pilot pressure has a spool valve shaft for switching the flow path, and a pilot solenoid valve in which pilot pneumatic pressure for driving the spool valve shaft is supplied and controlled to the spool valve shaft. Accordingly, a valve assembly is formed by the spool valve shaft and the pilot solenoid valve. Regarding the manifold solenoid valve in which the valve assembly is collectively connected to the base, formed in the base are a common pilot air-supply flow path for supplying pilot pressure to each pilot solenoid valve, and a common pilot exhaust flow path for exhausting the pilot pressure to the outside. The base of the manifold solenoid valve includes a divided type, and the divided type base is formed by connecting a plurality of base modules to each of which the valve assembly is attached.
The manifold solenoid valve mentioned above includes an internal pilot type and an external pilot type. The internal pilot type has a structure of: being branched from the common air-supply flow path of the base to supply, to the pilot air-supply flow path, part of the compressed air in the air-supply flow path; and supplying the compressed air in the air-supply flow path to the pilot solenoid valve. The external pilot type has a structure of: directly supplying the pilot pressure to the pilot flow path from the outside; and supplying the compressed air to the pilot solenoid valve from the outside. In the external pilot type, pressure different from pressure supplied to the air-supply flow path can be supplied as pilot pressure to move the spool valve shaft.
The manifold solenoid valve, in which an actuating mode of the pilot solenoid valve is switched to any of the internal and external pilot types, is described in Patent Document 1 (Japanese Patent Application Laid-Open Publication No. 11-141712), Patent Document 2 (Japanese Patent No. 2679934), and Patent Document 3 (Japanese Patent Application Laid-Open Publication No. 10-54473).